The present invention pertains to electrical immersion heaters and more particularly to immersion heaters which extend through the wall of a fluid-containing vessel.
In a wide variety of applications, it is convenient to heat fluid in a vessel or the like with an electrical immersion heater. Electric immersion heaters are the most widely used means of heating liquids such as water, oil, alkalis, chemical solutions, mild acids, electroplating solutions, salt solutions and many others. Immersion heaters dissipate substantially all of the heat produced by electrical energy conversion to the vessel. More specifically, immersion heating has 100% efficient electrical energy conversion where all heat is dissipated into the liquid. Immersion heaters commonly include a header or plug which extends through and is sealed in an opening in the fluid-containing vessel, a tubular casing or sheath which extends inward of the header and carries the heating elements, and a terminal box wherein the resistive element is electrically connected to external leads. Various other electrical components may also be disposed within the terminal boxes, for example, a thermostat that controls the temperature of the fluid.
The present invention is directed to providing a method which reduces manufacturing costs of a screw plug kind of immersion heater. The method and apparatus in accordance with this invention should reduce the cost of the screw plug used in the immersion heater by 35%-40%.
Some conventional screw plug bodies are manufactured by machining a bushing where about 60% of the bushing is machined away. When using an expensive metal, such as nickel or chrome metal, there is a desire not to waste 60% of the raw material in contouring the bushing to the desired shape.
It is a primary object of this invention to provide a new screw plug and a method of making the same inexpensively. These and other objects and advantages of the invention will become more apparent from the following detailed description and the appended claims.